Identification of a Highly Conserved Epitope on Avian Influenza Virus Non-Structural Protein 1 Using a Peptide Microarray

Applications of Peptide Microarrays in Autoantibody, Infection, and Cancer Detection

The diversity of the antigen-specific humoral immune response reflects the interaction of the immune system with pathogens and autoantigens. Peptide microarray analysis opens up new perspectives for the use of antibodies as diagnostic biomarkers and provides unique access to a more differentiated view on humoral responses to disease. This review focuses on the latest applications of peptide microarrays for the serologic medical diagnosis of autoimmunity, infectious diseases (including COVID-19), and cancer.

Rapid Response to Pandemic Threats: Immunogenic Epitope Detection of Pandemic Pathogens for Diagnostics and Vaccine Development Using Peptide Microarrays

Emergence and re-emergence of pathogens bearing the risk of becoming a pandemic threat are on the rise. Increased travel and trade, growing population density, changes in urbanization, and climate have a critical impact on infectious disease spread. Currently, the world is confronted with the emergence of a novel coronavirus SARS-CoV-2, responsible for yet more than 800 000 deaths globally. Outbreaks caused by viruses, such as SARS-CoV-2, HIV, Ebola, influenza, and Zika, have increased over the past decade, underlining the need for a rapid development of diagnostics and vaccines. Hence, the rational identification of biomarkers for diagnostic measures on the one hand, and antigenic targets for vaccine development on the other, are of utmost importance. Peptide microarrays can display large numbers of putative target proteins translated into overlapping linear (and cyclic) peptides for a multiplexed, high-throughput antibody analysis. This enabled for example the identification of discriminant/diagnostic epitopes in Zika or influenza and mapping epitope evolution in natural infections versus vaccinations. In this review, we highlight synthesis platforms that facilitate fast and flexible generation of high-density peptide microarrays. We further outline the multifaceted applications of these peptide array platforms for the development of serological tests and vaccines to quickly encounter pandemic threats.

A NS1-binding monoclonal antibody interacts with two residues that are highly conserved in seasonal as well as newly emerged influenza A virus

The non-structural protein 1 (NS1) of influenza A virus (IAV) is a multifunctional protein that antagonizes host antiviral responses, modulating virus pathogenesis. As such, it serves as a good target for research and diagnostic assay development. In this study, we have generated a novel monoclonal antibody (mAb) 19H9 and epitope mapping revealed that two residues, P85 and Y89, of NS1 are essential for interacting with this mAb. Furthermore, residues P85 and Y89 are found to be highly conserved across different IAV subtypes, namely seasonal H1N1 and H3N2, as well as the highly pathogenic H5N1 and H5N6 avian strains. Indeed, mAb 19H9 exhibits broad cross-reactivity with IAV strains of different subtypes. The binding of mAb 19H9 to residue Y89 was further confirmed by the abrogation of interaction between NS1 and p85β. Additionally, mAb 19H9 also detected NS1 proteins expressed in IAV-infected cells, showing NS1 intracellular localization in the cytoplasm and nucleolus. To our knowledge, mAb 19H9 is the first murine mAb to bind at the juxtaposition between the N-terminal RNA-binding domain and C-terminal effector domain of NS1. It could serve as a useful research tool for studying the conformational plasticity and dynamic changes in NS1.

Annexin A2 (ANXA2) interacts with nonstructural protein 1 and promotes the replication of highly pathogenic H5N1 avian influenza virus

BACKGROUND

Non-structural protein 1 (NS1) is a multifunctional protein and a crucial regulatory factor in the replication and pathogenesis of avian influenza virus (AIV). Studies have shown that NS1 can interact with a variety of host proteins to modulate the viral life cycle. We previously generated a monoclonal antibody against NS1 protein; In the current research study, using this antibody, we immunoprecipitated host proteins that interact with NS1 to better understand the roles played by NS1 in communications between virus and host.

RESULTS

Co-immunoprecipitation experiments identified annexin A2 (ANXA2) as a target molecule interacting with NS1. Results from confocal laser scanning microscopy indicated that NS1 co-localized with ANXA2 in the cell cytoplasm. Overexpression of ANXA2 significantly increased the titer of H5N1 subtype HPAIV, whereas siRNA-mediated knockdown of ANXA2 markedly inhibited the expression of viral proteins and reduced the progeny virus titer.

CONCLUSIONS

Our results indicate that ANXA2 interacts with NS1 and ANXA2 expression increases HPAIV replication.